One of the most controversial questions in sexual selection is what causes the evolution of female preference for certain male characteristics. Although these traits often seem arbitrary, it is usually assumed that the evolution of male traits can be explained by female preference for greater and greater development of those characters. However, it is not clear what benefits females obtain from choosing males with these traits. The two competing hypotheses are (1) that selective females produce male offspring that are also attractive to females or (2) that selective females obtain mates that contribute superior resources or superior genetic qualities to their offspring. The Trinidad guppy presents a unique opportunity to determine the natural selection payoffs that selective females obtain, because this species lives in areas with high and low levels of predation. This should produce variation in natural selection payoffs that will cause differences in female preference for exaggerated male characters important in determining predation risk. This will be the first study to use variation in natural selection, laboratory selection experiments, and breeding designs to determine how female preference and male traits coevolve by the process of sexual selection.
